Switching electrical power supply utilizing miniature inductors integrally in a PCB

Abstract

Electrical switching power supply for microprocessors and the like comprising a high voltage d.c. source (30, 34, 32, 50) resonant circuit (38, 51, 42, 52) including a switching transistor (52) which is operated in Megahertz range and provides pulses, via a transformer (40), rectifier (56), smoothing choke (62) to a d.c. low voltage output terminal (66). The rate of switching is controlled by a pulse generator (54) which pulses variably in response to output voltage to thereby vary switching repetition rate and hold to a predetermined output voltage. The inductive elements use spirals (12A and 12A') of thin lines on the surface of a substrate board and ferrite plugs (20) passing through holes (22) in the board to provide miniature inductive elements built into the substrate for effective use in a microprocessor power supply, or the like, and in other applications. Power dissipating elements on the circuit are mounted to a common thermal ground (29) and the circuit as a whole, including such thermal ground is encapsulated to provide a plate form power supply.

What is claimed is: 
     
       1. Electrical power supply comprising, in combination: (a) means for converting a line a.c. to d.c. and applying a resonant pulsation thereto at an operating frequency of at least 1.0 megahertz,   (b) means defining a transformer with primary and secondary windings formed on surface areas of printed circuit board (PCB) means with inductive coupling material passing through the PCB substrate at primary and secondary winding locations thereon, such material forming an essentially closed magnetic loop outside the PCB, the primary and secondary winding turn ratio being selected to provide voltage step-down, current step-up,   (c) means for applying said resonant pulsed d.c. to a transformer primary winding and applying a transformer secondary winding's induced pulse current to output terminals via rectifier and filter means, as a low voltage d.c.,   (d) said resonant circuit means comprising switching means therein to control the pulsed current applied to the primary winding of the transformer,   (e) voltage feedback means connected from the transformer secondary circuit to said resonant pulsation control switch to control pulsation,   and (f) means for establishing a common thermal plane of the heat generating components of said power supply including at least the magnetic loop defining means of said transformer.   
     
     
       2. Electrical power supply in accordance with claim 1 wherein the primary winding of the transformer comprises less than fifty turns with the cross section of each turn being of sharp cornered rectangular form within a recess of the PCB substrate. 
     
     
       3. The power supply of claim 1 wherein said switch is a solid state gated switch selected from the group consisting of bipolar and MOSFET-transistors, the said voltage feedback comprises an optical coupler connected to transmit the transformer means secondary voltage to operate switch driver means via a voltage controlled oscillator to produce a pulsing on and ringing off mode of switch operation. 
     
     
       4. The power supply of claim 3 wherein a MOSFET switch is used as said switching element. 
     
     
       5. An electrical power supply in accordance with claim 1 wherein the switching transistor is a bipolar transistor. 
     
     
       6. An electrical power supply in accordance with claim 1 wherein the switching transistor is a MOSFET transistor. 
     
     
       7. Electrical power supply in accordance with claim 6 wherein the system is constructed and arranged so that the operating frequency is at least 2.0 megahertz. 
     
     
       8. A switching power supply in accordance with claim 1 constructed and arranged to establish phase separation of voltage and current transitions at the transistor switch thereby reducing switching-interval dissipation to essentially zero. 
     
     
       9. A switching power supply in accordance with claim 1 wherein said inductive elements comprise spiral metallizations capable of carrying multiple ampere currents on at least one surface of the substrate. 
     
     
       10. A switching power supply in accordance with claim 9 wherein the substrate is of planar form and such spirals are provided on both surfaces of the substrate, opposite spirals being connected by ferromagnetic core elements passing through the spiral.